An organic light emitting device is formed by two opposing electrodes and organic material thin films having a plurality of layers having semiconductor-like properties interposed therebetween. The organic light emitting device having the aforementioned configuration uses a phenomenon in which electric energy is converted into light energy by using an organic material, that is, an organic light emitting phenomenon. Specifically, when voltage is applied between two electrodes in a structure in which an organic material layer is disposed between an anode and a cathode, holes from the anode and electrons from the cathode are injected into the organic material layer. When the injected holes and electrons meet each other, an exciton is formed, and the exciton falls down to a bottom state again to emit light.
In the aforementioned organic light emitting device, light generated from the organic material layer is emitted through a light-transmitting electrode, and the organic light emitting device may be typically classified into a top emission type, a bottom-emission type, and a dual emission type. In the case of the top emission or bottom emission type, one of two electrodes needs to be a light transmitting electrode, and in the case of the dual emission type, all the two electrodes need to be light transmitting electrodes.
In respect to the aforementioned organic light emitting device, many studies have been concentrated since Kodak Co., Ltd. announced that when a multilayer structure is used, the element may be driven at low voltage, and recently, a natural color display using the organic light emitting device is attached to a mobile phone and commercialized.
Further, as recent studies on the organic light emitting device using a phosphorescent material instead of an existing fluorescent material have been conducted, efficiency has been rapidly improved, and it is also expected that the element would be able to replace a known lighting in the near future.
In order to use the organic light emitting device as lighting, the element needs to be driven at high brightness unlike the existing natural color display, and constant brightness needs to be maintained like the existing lighting. In order to sufficiently improve the brightness of the organic light emitting device, light emission needs to be implemented in a large area, and in order to implement light emission in the large area, a high driving current needs to be used. In addition, in order to maintain the constant brightness in the large area, the aforementioned high current needs to be uniformly injected into the device having the large area.